1. Field of the Invention
The present invention relates to closures for food packaging. Specifically, the present invention relates to a one-piece flip-cap closure for use in food packaging having a tamper-evident structure thereon.
2. Description of the Related Art
Resealable closures are now commonly employed on, for example, gable-top containers. The closures are generally snap-type caps or screw-type caps which are removable from and resealable over an opening of a corresponding spout. Such closures desirably include tamper-evident features to enable a retailer or consumer to determine whether the closure has been opened before.
Conventional closures have certain limitations. For one thing, the closures themselves can be quite costly to produce, frequently being formed from two or more separate parts formed in two or more separate molds using two or more separate injection molding processes and two or more different materials. Even where a single mold is used, costly and complex laterally moving mold elements which move perpendicular to the primary mold closing direction may be required.
Another problem with many closures is the requirement for difficult and expensive assembly operations for finishing the closures and installing them on containers. These operations can require expensive tooling. Even the parts of a simple threaded cap and spout closure for installation through a panel of a gable top container must be separately molded, positioned in relation to each other, assembled, and then held in place in some fashion (such as by installing a tamper-evident joint at the same time) as the cap does not loosen and potentially fall off. These operations are conventionally carried out by the manufacturer of the closures, which are shipped in bulk to the food packager. The food packager must then retrieve each assembled closure from its bulk container, orient it in a packaging machine, and secure the closure to the package as it is assembled and (usually) before it is filled.
A closure with a snap-on cap joined to the spout by an integral hinge is somewhat easier to assemble, in that the cap and spout, and in some instances the tamper-evident structure, are already located in preestablished positions by molding them as one piece. But snap-on closures often require complex assembly and joining operations to initially close them and place their tamper-evident structure in its operative position. For mass-production closures, complex machinery is required to carry out the assembly operation. Too often, the closure must be assembled in one or more steps, closed in one or more steps, and installed on the container in one or more steps. The entire manufacturing process can thus include many steps, and many duplicate steps (such as multiple heat sealing operations conducted on different machinery at different times).
The closure assembly must be inserted cleanly through a relatively small aperture in the container when the closure is installed. Commonly, the spout, cap, tamper-evident structure, and other closure elements are inserted through an aperture slightly greater in diameter than the spout, from the inside of the container. If the parts of the closure are not tied securely together and properly located during assembly, one or more appendages of the closure can be dislocated. At a minimum this can result in rejected containers. Worse, the automated mechanism for assembling closures or containers can jam, necessitating a shut-down to correct the problem.
Closures are known which have an impervious membrane or web closing the spout before use and a tear ring located within the spout. In many instances, the tear ring is recessed in the spout, and can be grasped only by inserting a finger into it and pulling it out of the spout to tear and remove the membrane or web and open the spout for use. One difficulty with many such tear rings is that a person with large fingers, or a person using one of his or her larger fingers or a thumb, or a person lacking in dexterity, has difficulty inserting a finger in the recessed ring. The inaccessible edge of the recessed ring cannot be manipulated. The ring is thus difficult to lift out of place so it can be grasped more firmly.
If the entire ring is simply elevated above the mouth of the spout in the same orientation (usually, parallel to the membrane), space must be left under the entire cap to accommodate the elevated ring or tab, thus providing a high-profile closure which projects a substantial distance above the panel in which the closure is mounted. A high profile closure is undesirable, as it can be unsightly and may require more material than a low-profile closure of the same diameter. A high-profile closure mounted on a diagonal top panel of a gable-top container also may project through the plane of the side panel of the container, interfering with packing operations.
Another issue regarding closures is the desirability of forming a closure from polyethylene, which can be heat-sealed or ultrasonically sealed directly to a polyethylene coated paperboard panel or a polyethylene bottle, as opposed to forming the closure from another plastic which must be glued to polyethylene. Gluing is a less desirable and less sanitary assembly method than heat or ultrasonic sealing, in general.
While polyethylene closures are easily installed on polyethylene-coated paperboard and other surfaces by heat or ultrasonic welding, polyethylene has other characteristics which must be dealt with when designing a closure. For example, polyethylene, unlike polypropylene and other plastics, readily inelastically deforms or relaxes during storage, and thus has little springiness or "memory" of its configuration as molded.
For example, assume that a cap, spout, and integral hinge assembly is molded in an open configuration with the inverted cap beside the upright spout and the hinge straight, then the hinge is folded in a "U" shape to position the cap upright above the spout, and the cap is pushed down on the spout. Next, assume the closure is stored for a time, then installed on a container, which is filled, closed, transported, stored for another time, then finally placed in the hands of a consumer.
If the closure is made of polypropylene, when the consumer finally opens the closure, the hinge will be springy or have a "memory" of being open when it was originally molded. The cap will thus spring out of the way of the spout, and not block or be soiled by a stream of fluid contents poured from the spout of the container.
If, however, the closure is made in the same way of polyethylene, the plastic will have relaxed during storage and the cap will not spring out of the way of the spout to the desired degree when the closure is opened. This problem requires the consumer to make a special effort to hold the cap out of the way when dispensing the contents of the container, or to risk soiling the cap and thus providing an unsanitary or unsightly closure.
Accordingly, the inventors have recognized that a need remains within the industry for an improved closure which assists in overcoming the disadvantages experienced in the past and discussed above.